A freeform-based, fast, wide-field, and distortion-free camera for ultralow surface brightness surveys

Testing the predictions of galaxy formation scenarios on mildly- and non-linear regimes requires the detection from space of ultra-low surface brightness features both around galaxies (dwarf satellites) and in the cosmic web (filaments). The requirements of such a space mission imply innovative concepts for fast, wide-field, distortion-free telescopes. Several optical designs, based on freeform mirrors, are presented and compared here to address these stringent constraints on space-borne, wide field drift-scanning imaging. An optimal solution is presented, showing that a telescope with f /2, 4° × 2° FoV, with a 50 cm pupil can achieve the required exquisite image quality, free of distortion, with an optimal SNR in the detection of ultra-low surface brightness.